National Research Centre on Plant Biotechnology, New Delhi 110 012, India; Department of Bioscience and Biotechnology, Banasthali University, Tonk, Rajasthan 304 022, India.
National Research Centre on Plant Biotechnology, New Delhi 110 012, India.
Fungal Genet Biol. 2018 Jun;115:9-19. doi: 10.1016/j.fgb.2018.04.005. Epub 2018 Apr 6.
Rice and Magnaporthe oryzae constitutes an ideal pathosystem for studying host-pathogen interaction in cereals crops. There are two alternative hypotheses, viz. Arms race and Trench warfare, which explain the co-evolutionary dynamics of hosts and pathogens which are under continuous confrontation. Arms race proposes that both R- and Avr- genes of host and pathogen, respectively, undergo positive selection. Alternatively, trench warfare suggests that either R- or Avr- gene in the pathosystem is under balanced selection intending to stabilize the genetic advantage gained over the opposition. Here, we made an attempt to test the above-stated hypotheses in rice-M. oryzae pathosystem at loci of three R-Avr gene pairs, Piz-t-AvrPiz-t, Pi54-AvrPi54 and Pita-AvrPita using allele mining approach. Allele mining is an efficient way to capture allelic variants existing in the population and to study the selective forces imposed on the variants during evolution. Results of nucleotide diversity, neutrality statistics and phylogenetic analyses reveal that Piz-t, Pi54 and AvrPita are diversified and under positive selection at their corresponding loci, while their counterparts, AvrPiz-t, AvrPi54 and Pita are conserved and under balancing selection, in nature. These results imply that rice-M. oryzae populations are engaged in a trench warfare at least at the three R/Avr loci studied. It is a maiden attempt to study the co-evolution of three R-Avr gene pairs in this pathosystem. Knowledge gained from this study will help in understanding the evolutionary dynamics of host-pathogen interaction in a better way and will also aid in developing new durable blast resistant rice varieties in future.
水稻和稻瘟病菌构成了研究禾谷类作物中寄主-病原体相互作用的理想病理系统。有两种替代假说，即军备竞赛和堑壕战，它们解释了宿主和病原体的协同进化动态，这些宿主和病原体处于持续的对抗中。军备竞赛假说认为，宿主和病原体的 R-和 Avr-基因分别经历正选择。或者，堑壕战假说表明，病理系统中的 R-或 Avr-基因受到平衡选择的影响，旨在稳定相对于对手获得的遗传优势。在这里，我们试图在水稻-稻瘟病菌病理系统中检验上述三个 R-Avr 基因对的三个基因座（Piz-t-AvrPiz-t、Pi54-AvrPi54 和 Pita-AvrPita）的假设，使用等位基因挖掘方法。等位基因挖掘是一种有效的方法，可以捕获存在于群体中的等位基因变体，并研究在进化过程中对变体施加的选择压力。核苷酸多样性、中性统计和系统发育分析的结果表明，Piz-t、Pi54 和 AvrPita 在其相应基因座上是多样化的，并受到正选择，而它们的对应物 AvrPiz-t、AvrPi54 和 Pita 是保守的，并受到平衡选择的影响，这在自然界中是普遍存在的。这些结果表明，水稻-稻瘟病菌种群至少在研究的三个 R/Avr 基因座上进行堑壕战。这是首次尝试在该病理系统中研究三个 R-Avr 基因对的共同进化。从这项研究中获得的知识将有助于更好地理解宿主-病原体相互作用的进化动态，并有助于未来开发新的持久抗稻瘟病的水稻品种。
